In fact, I haven't written informations about the command fec 
fec is used to plot contour level of a function defined 
on a mesh constituted of triangles 
and assuming that f is linear on triangles 

The best way to undersantd how it works is to look at the two demo
files in demos/fec ( and source code for fec in routines/graphics/Fec )

===================================================================
fec.ex1 is a simple demo file in which a mesh and a function 
on that mesh is completely built in Scilab syntax 

Fec is used as folows : 
	let no be the number of nodes 
	and Ntr the number of traiangles 

fec(x,y,triangles,func,no,Ntr,strflag,legend,brect,aaint) 

	x and y are two vectors of size no 
		 (x(i),y(i)) gives the coordinates of node i 
	func is also a vector of size no : 
		 func(i) gives the value of the function for which we want
		the level curves.

	trianles : is a [Ntr,5] matrix 
		each line of triangles specifies a triangle of the 
		mesh 
		triangle(j) = [number,node1,node2,node3,flag]
		node1,node2,node3 : are the number of the nodes 
		which constitues triangle(j)
		number : is the number of the triangle 
		flag is an integer not used in the fec function 

	for the remaining arguments 
	strflag,legend,brect,aint : see plot2d 
===================================================================

fec.ex2 is an example for which the mesh and the function value where 
computed by an external `mesh builder    (amdba type mesh) and external program 
A set of macros ( provided in file fec_demos.sci) were used to read the to data files in Scilab 
and plot the results 
